1. Field of the Invention
The present invention relates to an anti-viral agent containing a modified and low-molecular weight .beta.-1,3-glucan having a very potent anti-human immunodeficiency virus (anti-HIV) activity.
2. Description of the Background
It is known that inorganic ion-containing organic high polymer compounds are effective for the prevention and treatment of retroviral infectious diseases. See, for example, Japanese Patent Application Laid-Open No. 62-215529. In particular, sulfates of polysaccharides are also known to be effective therefor. See, for example, Japanese Patent Application Laid-Open No. 63-45223. However, the anti-HIV activity of these compounds is not well understood. Moreover, the necessary structure thereof appears to be correlated to a blood anti-coagulating activity which is also manifested. This anti-coagulating activity is, of course, undesirable in the use of the compounds. Unfortunately, practically useful sulfated polysaccharides, without the above side effects, are not presently available.
Further, with respect to the method of sulfating polysaccharides, and the method of isolating the sulfated polysaccharides, a detailed investigation has been conducted with a dextran sulfate of .alpha.-1,6-glucan (Carbohydrate Research, 21 (1972), 420-426), but a detailed investigation on .beta.-1,3-glucan has not yet been conducted.
Thus, at present, a need continues to exist for compounds which exhibit a more potent anti-HIV activity, but which also have a reduced anti-coagulating activity. It would also be desirable to develop such compounds having fewer impurities than are found in conventional agents for HIV therapy.